Confinement Effect Emission from Infiltrated ZnO in PS-b-PMMA Nanostructures

TL;DR

This study investigates the growth and photoluminescence properties of infiltrated ZnO nanostructures within PS-b-PMMA block copolymers, revealing quantum confinement effects and defect-related emissions relevant for photonics.

Contribution

It demonstrates the controlled growth of ZnO nanostructures in PS-b-PMMA with size-dependent emission properties and highlights the influence of seed layers on defect states.

Findings

Blue-shifted emission at 335 nm indicates quantum confinement.

Seed layers introduce defect state emissions at 470 nm and 520 nm.

ZnO nanostructures exhibit uniformity and size control advantageous for photonic applications.

Abstract

We have characterized the growth of ZnO using sequential infiltration synthesis (SiS) on PS-b-PMMA block copolymers (BCP) of spherical and cylindrical sub-20nm morphologies and studied how the photoluminescence of these nanostructures varies per its seed layer. Investigation of these structures was done using atomic force microscopy (AFM), spectrofluorometry, Raman spectroscopy, and scanning electron microscopy (SEM). We report blue-shifted photoemission at 335 nm (3.70 eV), suggesting quantum confinement effects. This UV-photoluminescence can be translated into emitter sizes of roughly 1.5nm in radius. Furthermore, samples of ZnO prepared with an alumina seed layer showed additional defect state photoemission at 470 nm and 520 nm for spherical and cylindrical BCP morphologies, respectively. Defect photoemission was not observed in samples prepared without a seed layer. Raman and EXAFS data suggest lack of long range order between the ZnO nanostructures during early stages of infiltrated ZnO growth and therefore supports the blue shift emission is due to confinement. Our work demonstrates that ZnO nanostructures grown on PS-b-PMMA via infiltration are advantageous in uniformity and size, and exhibit unique fluorescence properties. These observations suggest that infiltrated ZnO in PS-b-PMMA nanostructures lends itself to a new regime of applications in photonics and quantum materials.